Full wave rectifier



2, 1932- w. L. KRAHL FULL WAVE RECTIFIER Filed Aug. 5, 1927Z-Sheets-Sheet 1 INVENTOR MINE/e .4. kfi'Al-IL ATTORNEY Aug. 2, 1932. w,L, KRAHL 1,869,567

FULL WAVE RECTIFIER Filed Aug. 5. 1927 2 Sheets-Sheet 2 INVENTOR WALTERL. ARxmm ATTORNEY Patented Aug. 2, 1932 UNITED STATES PATENT OFFICEWALTER LOUIS KRA HL, OF-MONTCLAIR, NEW JERSEY, ASSIGNOR TO ABCTURUS RADIO TUBE COMPANY, OF NEWARK, NEW JERSEY, .A CORPORATION OF DELAWAREFULL WAVE ancrrrmza Application filed August 5, 1927. Serial No.210,809.

This invention relates to rectifiers and particularly those adapted torectify both sides of an alternating current wave. 7

One of the objects of the invention is to provide a full wave rectifierwhich may be confined within a single glass envelope.

Another object of the invention is to pro-v vide a full wave rectifierin which a plurality of anode plates cooperate with a single cathode torectify both sides of the alternating current wave.

Another object of the invention is to provide means to reduce the creeage effect hetween'the conductors of a recti er.

Another object of the invention is to provide a full wave rectifier tubein which the various parts are compact and the terminal contacts ofwhich are all mounted in the base of the tube.

Other objects, and especially those related to economies of manufacturewill be apparent as the description of the invention proceeds.

One'embodiment of the invention has been illustrated in the accompanyingdrawings, in which Fig. 1 is a perspective view partly in sec- 7 tion ofa tube embodying my invention; and

Figs. 2 and 3' are diagrammatic views of circuits in which my improvedtube may be i used.

The rectifier tube has been illustrated as comprising an envelope 10sealed to a stem 11 in the usual manner and cemented in a base 12 bywhich the tube is adapted to be supported. A cathode 13 is supportedfrom the stem 11 in the following manner A short conductor wire 14 issealed into the upper end of the stem-and forms a support for the lowerend of the cathode 13, While the upper end of the cathode is supportedby a relatively longer conductor wire 15 which is also sealed in theupper end of the stem 11, and which is bent outwardly and upwardly,terminating at a point adjacent the top of the envelope 10. A connection16 from the top of the cathode 13 is welded or otherwise attached to theupper end of the support 15.

The cathode is preferably formed in the shape of a hollow cylinder, andmay be atment is attached at its lower end to a short conductor support20, and at its upper end to a thin, flat spring 21 which is in turnwelded to the upper end of the support 15 and extends transverselythereto. The filament 19 is preferably composed of carbon, first platedwith copper, and then plated with nickel, which permits it to be readilywelded to the support 20 at the bottom and the spring 21 at the top. Thespring 21 tends to draw the filament 19 upwardly and thereby maintainsthe filament spaced from the cathode, compensating for changes intemperature when the tube is out into and out of service.

A pair of anode plates 22 are supported-adjacent the cathode 13, butspaced therefrom. These plates, which may be formed of nickel,molybdenum or the like are preferably semicylindrical in form, eachbeing composed of two quarter cylindrical sections 23 and 23a with fiatprojections 24 and 25 riveted or otherwise attached together so thatwhen placed on opposite sides of the'cathode 13, the plates aresubstantially parallel to the surface of the cathode. In order tosupport the plates 22, I have provided wires 28 and 29 which enter tubes25a, formed in the flat plate projections 24 and'25 and are weldedthereto, and which are bent backwardly and downwardly and secured attheir lower ends to a glass head 30. The lower ends of the plates 22 aresupported by the lead wires 26 and 27 which are sealed into the stem andwhich extend into the lower ends of the tubes 25a formed in the flatplate projections 24 and 25 and are welded therein.

In order to reduce to a minimum any tendenc for creepage from theconductors 26 I an 27 where'they are sealed in the stem 11, I haveprovided two glass tubes 31 and 32 around the wires 26 and 27, resectively, and melted into the upper part 0 the stem 11. This may veryeasily be done when the wires are sealed into the neck by placing thetubes 31 and 32 around their respective wires before the upper end ofthe stem is pressed into position. The glass tubes 31 and 32 extendupwardly a short distance and therefore greatly increase the surfacedistance on the glass from the wires 26 and 27 to the other conductorssealed in the stem 11.

The various connections to the parts of the rectifier are all madethrough the base 12 of the tube. To this end, contact terminals 33,34/35 and 36 are embedded in the base and extend downwardly therefrom inthe usual manner. The terminals 33 and 34 are connected respectively tothe conductors 20 and 15 and therefore connect with the lower and upperends of the filament 19, and the filament therefore may be energized bypassing acurrent through the terminals 33 and 34. The lower cathodesupport 14 is connected to the terminal 34, while the upper end of thecathode is connected by means of the strip 17 and the connector 16 tothe upper end of the support 15 which is also connected to the terminal34, thus connecting both the upper and lower end of the cathode to thesingle terminal 34. The plate supports 26 and 27 are connectedrespectively to the terminals 35 and 36, as will be seen from Fig. 1.

In Figs. 2 and 3'of the drawings, two circuit diagrams havebeen shown,illustrating the manner in which the rectifying tube may be connected ina circuit. In Fig. 2, a transformer 37 is provided having a primary coil38 adapted to be connected to a source of alternating current, andsecondary coils 39 and 40. The secondary coil 40 has a limited number ofturns, and is connected to the two terminals 33 and 34, so that thefilament 19 may be energized by alternating current at reduced voltage.The coil 39 may be connected to the plates 22 and 23 through theterminals 35 and 36 respectively. A tap 41 is provided at the center ofthe secondary coil 39, and is connected to the terminal 34.

In the operation of the device when the transformer is energized,alternating current is induced in the coil 39, but owing to the factthat electron emission will only occur from the cathode 13 to the plates22 and 23, current will flow in the leads between the plates 22 and 23,and the ends of the coil 39, in one direction only. In Fig. 2 the loads42 and 43 have been shown in the circuits of the plates 22 and 23respectively, and also filters 44 and 45, where such filters aredesirable. This type of circuit may be advantageously emplaved in aradio circuit for an eliminator or other devices requiring rectifiedcurrent.

In Fig. 3 a similar circuit is shown with the exception that the load 46is shown in the connection between the tap 41 on the secondary coil 39and the terminal 34 of the tube. A filter 47 may also be used ifdesired. This arrangement may be used wherever a single circuit ofrectified current is required.

The cylindrical cathode insures a steadier electron emission. This isbecause the electron emission is controlled by the heatof the cathodeand the greater the mass of the cathode the less variation of heat therewill be and hence this tube will provide a more even flow of currentthan ifan ordinary filament were used for the cathode.

It will be noted that I have provided a rectifying tube which willrectify both sides of the alternating current wave, and which iscompact, easily manufactured, and the terminals of which are all mountedin the base of the tube. 2

In my application, Serial No. 140,245 for vacuum tubes, filed October 8,1926, I have shown a vacuum tube adapted to be used for radio use, andwhich is adapted to take alternating current directly from the electriclight circuit. This tube has a filament and cathode similar to the tubeof the present invention and acylindrical plate adapted to fit aroundthe cathode similar to the plates in the present invention. Themanufacture of the rectifying tube may be very advantageously carried onin connection with the tubes described in the application above referredto, inasmuch as the only changes necessary are the elimination of thegrid from that tube and the splitting of the cylindrical plate into twohalves and the provision of a separate supporting means for one of theplates so formed.

While I have described and illustrated one form of the invention, manymodifications and changes in the construction thereof may be resorted towithout departing from the spirit of the invention, and I do not desireto limit myself, therefore, to the specific construction shown, but tointerpret the invention broadly, limited only by the appended claims.

Having thus described my invention, what I desire to claim is 1. Arectifier tube comprising a stem; aconductor extending through said stemand supported thereby; a cylindrical cathode mounted upon saidconductor; a pair of conductors adjacent said first conductor, extendingthrough said stem and supported thereby; a semi-cylindrical anodesupported on each of said conductors adjacent said cathode but spacedtherefrom and from each other, each of said anodes comprising a. pair ofplates having flanges and secured together III by means of said flanges;means comprising an insulating member for maintaining the opposite endsof said anodes in spaced relation; and an atmosphere of greatly reducedpressure surrounding said cathode and anodes.

2. A rectifier tube comprising astem; a conductor extending through saidstem and supported thereby; a cylindrical cathode mounted upon saidconductor; a pair of conductors adjacent said first conductor, extendingthrough said stem and supported thereby; a semi-cylindrical anodesupported on each of said conductors adjacent said cathode but spacedtherefrom and from each other, each of said anodes comprising a pair ofquarter-cylindrical plates each having a longitudinal flange at one sidethereof, said plates being secured together by said flanges,

means comprising an insulating member for maintaining the opposite endsof said anodes in spa ed relation; and separate means to heat saidcathode.

3. In a rectifier tube comprising a stem; a

conductor sealed in said stem; a cylindrical cathode, one end of whichis attached to and suppo ted by said conductor; a second conductorsealed in said stem and attached to the other end of said cathode; anadditional pair 39 of conductors sealed in said stem; a semicylindricalanode plate attached to each of said additional conductors, said platescomprising a pair of quarter-cylindrical plates each having a radialflange longitudinally extending on one side thereof, said plates beingsecured together by said flanges; an insulating member attached to oneof said first mentioned conductors; a pair of supports connected to saidinsulating member and the 4 other end of said anode plates, said platesbeing spaced from each other and from said cathode and substantiallyconcentric with the latter; and means for separately heating saidcathode.

4. In a rectifier tube, a cylindrical cathode;

means to support said cathode; a pair of semi-cylindrical plates onopposite sides of said cathode and spaced therefrom-and from each other,but substantially concentric there- 60 with, said plates each comprisinga pair of quarter-cylindrical plates having a longitudinal flanges onone side thereof extending in a direction radial to the center ofcurvature of the plate, said plates being held together portions of theflange of one plate extending through openings in the flange of theother plate and being bent over on the other side thereof; and aseparate heater for said cathode.

6 In testimony whereof, I aflix my signature.

- WALTER L. KRAHL.

